Abstract: The canopy and leaf hyperspectral reflectance of three spring wheat cultivars at their different growth stages and with seven planting densities were measured in field during April and August 2006. It was found that at booting stage, the canopy and leaf reflectance of spring wheat under the 7 planting densities was distinctly different, though the wave shapes were similar. Meanwhile, the canopy spectral reflectance decreased with increasing planting density in visible (VIS) region but increased in near infrared (NIR) region at booting stage, while this change was not evident and the difference in VIS region was less than that in NIR region at ripening stage. The change of leaf reflectance under different planting densities showed coherence in VIS and NIR regions at different growth stages, but the change with planting density was not clear. The canopy reflectance was higher at ripening than at booting stage; while the leaf reflectance in NIR region was higher at booting than at ripening stage. There were some differences for different spring wheat cultivars at canopy and leaf level. At booting stage, the difference of canopy spectral reflectance among different cultivars was less in VIS region but obvious in NIR and shortwave infrared regions, while the difference at ripening stage was less. The difference of leaf spectral reflectance among different cultivars was obvious in NIR region. There existed “double peak” phenomena for the spring wheat at vegetative growth stage. Additionally, there existed a ‘blue shift’ phenomenon for the position of red edge (λ_red), and the slope of red edge (D_λred) and the area of red edge (S_red) at canopy- and leaf level were decreased from booting to ripening stage, suggesting that the λ_red change could be used to estimate wheat yield, and S_red could be the indicator of wheat growth stage.

Key words: Taklamakan Desert, Tamarix ramosissima, Populus euphratica, Water potential